Method and means for controlling the delivery of liquid to spray guns

ABSTRACT

Delivery of liquid to spray guns is controlled by supplying the pump motor of the spray gun with air under substantially unchanged pressure while reducing in a liquid pressure reduction valve the pressure of the liquid delivered from the pump, and loading the liquid pressure reduction valve by selective air pressure taken from an air pressure reduction valve. Both positive and negative pressure pulses of a reciprocating pump are suppressed.

United States Patent Liedberg et a1.

[15] 3,692,214 [4 1 Sept. 19, 1972 [s41 METHOD AND'MEANS FOR CONTROLLING THE DELIVERY OF LIQUID T0 SPRAY GUNS Inventors: Kurt Herman Lie'dberg; Nils Erik Reinhold .lonsson; Sten Gunnar Hugo Svensson, all of Skara, Sweden Atlas Copco Aktiebolag, Nacka, Sweden Filed: May 12, 1970 Appl. No.: 36,509

[73] Assignee:

US. Cl. ..222/334, 222/385, 239/332 Int. Cl ..G0lf 11/00 Field of Search ..222/384, 385, 334, 310, 382,

References Cited UNITED STATES PATENTS 2,763,513 9/1956 Paradise ..222/334 x 2,751,114 6/1956 Greaves ..222/3 10 X 2,943,765 7/1960 Glascow et al ..222/383 X 3,023,968 3/ 1962 Mitchell ..239/267 X 3,219,276 11/1965 Norris ..239/1 86 Primary ExaminerRobert B. Reeves Attorney-Bauer & Goodman ABSTRACT Delivery of liquid to spray guns is controlled by supplying the pump motor of the spray gun with air under substantially unchanged pressure while reducing in a liquid pressure reduction valve the pressure of the liquid delivered from the pump, and loading the liquid pressure reduction valve by selective air pressure taken from an air pressure reduction valve. Both positive and negative pressure pulses of a reciprocating pump are suppressed.

5 Clairus, 2 Drawing Figures PATENTEDSEP 19 \972 I 3.692.214 SHEET 2 OF 2.

FIG. 2

METHOD AND MEANS FOR CONTROLLING THE DELIVERY OF LIQUID TO SPRAY GUNS The invention relates to method and means for controlling the delivery of liquid to spray guns in which spraying liquid is delivered to the spray gun at adjustable quantity from a pump actuated by a compressed air driven motor. The dosage of liquid in such spray guns normally is performed thereby that one varies the air pressure active on the motor of the pump. That method is exposed to disturbances by reason of the pressure reduction eventually causing jolting in the operation of the pump, leading to undesired pulsations in the liquid flow and being able to cause interruptions in operation of the pump motor because of jamming of the air distribution mechanism. The pressure of the liquid delivered by the pump is furthermore normally measured by a manometer which is in direct contact with the liquid and has to be cleaned after use in connection with interruptions of operation or exchange of liquid.

It is an object of the invention to provide a method for controlling the delivery of liquid to spray guns and a means for controlling such delivery for performing said method, in which one assures that the drive motor of the pump works under substantially unchanged drive air pressure during all delivery so that the operation of the pump will not be disturbed by control of the liquid delivery. A further object of the invention is to provide an efficient and simple control of the liquid delivery by selective pneumatic loading of a pressure reduction valve for the liquid. A still further object of the invention is to assure that the liquid pressure shall be measurable without the measuring manometer having to be set into contact with the liquid.

For the above and other purposes there is according to one aspect of the invention presented a method for controlling the delivery of liquid to spray guns supplied with spraying liquid at adjustable quantity from a pump actuated by a compressed air driven motor, said method comprising the steps of supplying the motor with compressed air from a source of compressed air at substantially unaltered pressure during delivery, taking compressed air from said compressed air source at selectively reduced pressure, and reducing with said selectively reduced air pressure as a load the pressure of the liquid delivered from the pump. According to another aspect of the invention there is provided means for controlling the delivery of liquid to spray guns comprising a spray gun, a liquid supply pump, a liquid supply connection connecting said pump to said spray gun, a compressed air actuated motor for driving said pump, a source of compressed air connected to said motor, a liquid pressure reduction valve in the liquid supply connection between said pump and said spray gun, compressed air actuated loading means in said liquid pressure reduction valve for adjusting the pressure of the spraying liquid delivered to said spray gun, and a selectively adjustable air pressure reduction valve connected to said compressed air source and to said loading means for loading the latter by a selective air pressure.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which two embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that various modifications thereof may be made within the scope of the appended claims.

In the drawings FIG. 1 shows a means for controlling the delivery of liquid in connection with spray guns working according to the method of the invention.

FIG. 2 shows diagrammatically the corresponding method and means in connection with multiple spray guns.

On a liquid container 10 is mounted a pump 11 for delivering liquid under pressure from the container 10 by the aid of a reciprocating pump piston 12, which in the pump 11 drives liquid, preferably paint, upward to a delivery nipple 13. The pump 11 is driven by a compressed air motor 15 in which a drive piston 16 is set into reciprocating movement by actuation of compressed air, the distribution of which in the motor 15 is controlled by a distributing valve 17 causing movement of the drive piston 16 and the pump piston 12. The motor 15 is supplied with pressure fluid from a suitable compressed air source 18 via a conduit 19.

On the delivery nipple 13 is mounted a liquid pressure reduction valve 20 in which a diaphragm 21 separates a liquid chamber 22 and an air chamber 23. To the diaphragm 21 is affixed a reduction valve body 24 which coacts with a seat 25 at the outer end of the nipple 13 and opens against the direction of fluid flow therein. By means of a conduit 26 the liquid chamber 22 is connected to a liquid entry nipple on a spray gun 27 which in a spray nozzle provided forwardly on the gun 27 by the aid of compressed air in well-known manner atomizes the liquid entering from the conduit 26. The air is received from the source 18 via a conduit 28 connected to the air nipple of the spray gun 27. The diaphragm 21 of the liquid pressure reduction valve 24 isloaded by air pressure in the air chamber 23 and the pressure therein is adjusted selectively by the aid of a manually adjustable air pressure reduction valve 30 which likewise is connected to the compressed air source 18 for example by means of a portion of the conduit 19.

The diaphragm 21 in the housing of the liquid pressure reduction valve 20 provides a pressure balancing means which on the one hand is actuated by liquid pressure in the liquid chamber 22 and on the other by the adjusted air pressure in the air chamber 23. The latter is measured by the aid of a manometer 31 connected to the air chamber 23. Obviously the air pressure measured by the manometer exactly corresponds to the liquid pressure in the liquid chamber 22 and one thus obtains a reading of the liquid pressure delivered without setting the manometer 31 into contact with the liquid. By the aid of the air pressure reduction valve 30 there is obtained the desired adjustment of the liquid delivery pressure and thereby of the quantity of liquid delivered from the pump 11 without having to actuate the drive pressure of the pump motor 15.

The liquid chamber 22 in the path of the liquid flow from the pump 11 to the spray gun 27 coacts with the air loaded diaphragm 21 to also suppress negative pressure pulses of the reciprocating pump 1 1.

In the embodiment of FIG. 2, two or multiple spray guns 27, 27", 27" are connected to the same pump 11. To the delivery nipple 13 thereof is connected a conduit 32 which branches into branches 33-33" each connected to a liquid pressure reduction valve 20 40". The valves 20-20 are made in analogy with valve 20 in FIG. 1 and each of them is connected to one of the spray guns 2727? via a liquid conduit 2626 All liquid pressure reduction valves 2020" are loaded by a common compressed air pressure which is transmitted via a conduit 34 from a single manually adjustable air pressure reduction valve 30 connected to the compressed air source 18.

In connection with the arrangement in FIG. 2, by the air pressure reduction valve 30 suitably located on a control board for the spraying plant, the dosage of liquid is selevtively adjusted to one and the same value of adjustment in common and simultaneously for the whole group of spray guns 2 7-27 This is particularly advantageous for example during spraying of car bodies when a plurality of operators are spraying simultaneously and the required results are identical for all the spraying guns set in operation.

We claim:

l. A method for controlling the delivery of liquid to a spray gun comprising:

supplying spraying liquid to said spray gun at adjustable quantities from a reciprocating pump actuated by a compressed air driven motor;

supplying the compressed air motor with compressed air from a source of compressed air at substantially constant pressure during delivery;

taking compressed air from said compressed air source at a selectively reduced air pressure;

reducing, as a function of said selectively reduced air pressure as a load pressure, the pressure of the liquid delivered from the pump; and

balancing said load pressure by the liquid pressure in a liquid containing chamber in the path of the liquid delivered from the pump after reducing the pressure of the liquid delivered from the pump, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures.

2. Apparatus for controlling the delivery of liquid to a spray gun comprising:

a spray gun;

a reciprocating liquid supply pump;

a liquid supply connection connecting reciprocating pump to said spray gun;

a compressed air actuated motor for driving said reciprocating pump;

a source of compressed air connected to said air motor;

a liquid pressure reduction valve in the liquid supply connection between said reciprocating pump and said spray gun, said liquid pressure reduction valve including a valve housing, a valve seat in said valve housing, and a valve body cooperating with said valve seat and adapted to open in said valve housing in a direction opposite to the direction of liquid supply by said reciprocating pump;

compressed air actuated loading means in said liquid pressure reduction valve for adjusting the pressure of the spraying liquid delivered to said spray gun, said loading means being coupled to said valve body downstream of said valve seat and including a balancing means defining a liquid containing said chamber downstream of said valve seat and in said valve housing for balancing the pressure of the spraying liquid in said liquid containing chamber downstream of said valve seat by pressure of compressed air after the air pressure reduction valve, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures; and

a selectively adjustable air pressure reduction valve connected to said compressed air source and to said loading means for loading said loading means by a selected value of air pressure.

3. Apparatus for controlling the delivery of liquid to spray guns comprising:

a plurality of spray guns;

a reciprocating liquid supply pump;

liquid supply connections connecting reciprocating pump to said spray guns;

a compressed air actuated motor for driving said reciprocating pump;

a source of compressed air connected to said air motor; liquid pressure reduction valves in respective liquid supply connections between said pump and said spray gun, each of said liquid pressure reduction valves including a valve housing, a valve seat in said valve housing, and a valve body cooperating with said valve seat and adapted to open in said valve housing in a direction opposite to the direction of liquid supply by said reciprocating P p;

compressed air actuated loading means in each respective liquid pressure reduction valve for adjusting the pressure of the spraying liquid delivered to each said spray gun, each loading means being coupled to its respective valve body downstream of its respective valve seat and including a balancing means defining a liquid containing chamber downstream of said valve seat and in said valve housing for balancing the pressure of the spraying liquid in said liquid containing chamber downstream of said valve seat by pressure of compressed air after the air pressure reduction valve, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures; and

a single selectively adjustable air pressure reduction valve connected to said compressed air source and to all of said loading means for loading all said liquid pressure reduction valves by a single selected value of air pressure.

4. Apparatus according to claim 2 in which said pres sure balancing means comprises a diaphragm dividing said valve housing into said liquid containing chamber included in said liquid supply connection between said reciprocating pump and spray gun and a compressed air chamber connected to said air pressure reduction valve.

5. Apparatus according to claim 4 in which a manometer is connected to said compressed air chamber for measuring of the pressure of the liquid supplied to the spray gun without contacting the liquid.

i I it II said 

1. A method for controlling the delivery of liquid to a spray gun comprising: supplying spraying liquid to said spray gun at adjustable quantities from a reciprocating pump actuated by a compressed air driven motor; supplying the compressed air motor with compressed air from a source of compressed air at substantially constant pressure during delivery; taking compressed air from said compressed air source at a selectively reduced air pressure; reducing, as a function of said selectively reduced air pressure as a load pressure, the pressure of the liquid delivered from the pump; and balancing said load pressure by the liquid pressure in a liquid containing chamber in the path of the liquid delivered from the pump after reducing the pressure of the liquid delivered from the pump, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures.
 2. Apparatus for controlling the delivery of liquid to a spray gun comprising: a spray gun; a reciprocating liquid supply pump; a liquid supply connection connecting said reciprocating pump to said spray gun; a compressed air actuated motor for driving said reciprocating pump; a source of compressed air connected to said air motor; a liquid pressure reduction valve in the liquid supply connection between said reciprocating pump and said spray gun, said liquid pressure reduction valve including a valve housing, a valve seat in said valve housing, and a valve body cooperating with said valve seat and adapted to open in said valve housing in a direction opposite to the direction of liquid supply by said reciprocating pump; compressed air actuated loading means in said liquid pressure reduction valve for adjusting the pressure of the spraying liquid delivered to said spray gun, said loading means being coupled to said valve body downstream of said valve seat and including a balancing means defining a liquid containing chamber downstream of said valve seat and in said valve housing for balancing the pressure of the spraying liquid in said liquid containing chamber downstream of said valve seat by pressure of compressed air after the air pressure reduction valve, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures; and a selectively adjustable air pressure reduction valve connected to said compressed air source and to said loading means for loading said loading means by a selected value of air pressure.
 3. Apparatus for controlling the delivery of liquid to spray guns comprising: a plurality of spray guns; a reciprocating liquid supply pump; liquid supply connections connecting said reciprocating pump to said spray guns; a compressed air actuated motor for driving said reciprocating pump; a source of compressed air connected to said air motor; liquid pressure reduction valves in respective liquid supply connections between said pump and said spray gun, each of said liquid pressure reduction valves including a valve housing, a valve seat in said valve housing, and a valve body cooperating with said valve seat and adapted to open in said valve housing in a direction opposite to the direction of liquid supply by said reciprocating pump; compressed air actuated loading means in each respective liquid pressure reduction valve for adjusting the pressure of the spraying liquid delivered to each said spray gun, each loading means being coupled to its respective valve body downstream of its respective valve seat and including a balancing means defining a liquid containing chamber downstream of said valve seat and in said valve housing for balancing the pressure of the spraying liquid in said liquid containing chamber downstream of said valve seat by pressure of compressed air after the air pressure reduction valve, whereby pulsations inherently generated during operation of the reciprocating pump are suppressed by the balancing between the liquid and load pressures; and a single selectively adjustable air pressure reduction valve connected to said compressed air source and to all of said loading means for loading all said liquid pressure reduction valves by a single selected value of air pressure.
 4. Apparatus according to claim 2 in which said pressure balancing means comprises a diaphragm dividing said valve housing into said liquid containing chamber included in said liquid supply connection between said reciprocating pump and spray gun and a compressed air chamber connected to said air pressure reduction valve.
 5. Apparatus according to claim 4 in which a manometer is connected to said compressed air chamber for measuring of the pressure of the liquid supplied to the spray gun without contacting the liquid. 